Gauge converted

In rail transport, gauge conversion is the process of converting a railway from one rail gauge to another, by altering the railway tracks. An alternative to gauge conversion is dual gauge track, or gauge conversion of the rail vehicles themselves.

Rails may be too light for the loads imposed by broader-gauge rail cars and need to be replaced with a heavier rail profile.

If the conversion involves the track gauge being narrowed, the existing sleepers can often still be used, but if the gauge is being increased, the sleepers used for the narrower gauge may be too short, and need to be replaced with longer ones.

In some cases, gauge-convertible sleepers are installed before the conversion of the track itself. The sleepers must be long enough to take the wider of the two gauges, and must be able to accommodate the fittings for both the existing and the new gauges. In cases where the difference between the two gauges is small, such as 1,000 mm (3 ft 3 ³⁄₈ in) and 1,067 mm (3 ft 6 in) track, or 1,435 mm (4 ft 8 ¹⁄₂ in) and 1,524 mm (5 ft) track, providing dual-gauge track using a third rail is not practical. In those cases, gauntlet track is required.

During the conversion of the Melbourne–Adelaide railway in Australia from 5 ft 3 in (1,600 mm) to 4 ft 8 ¹⁄₂ in (1,435 mm), dual-gauging of the track was not possible because the foot of the heavy rails being used was too wide to allow them to be placed sufficiently close together. A special gauge-convertible sleeper, with a reversible chair for the Pandrol clip, allowed a two-week conversion process.

In June 2008, the South Australian government announced that by 2012 the Adelaide metropolitan network would be converted from 1,600 mm broad gauge to standard gauge. Consequently, broad-gauge timber sleepers are progressively being replaced with gauge-convertible concrete sleepers on the metropolitan rail network. As of 2016^[update], however, gauge conversion had not commenced, and financial constraints seem likely to delay the program for the foreseeable future.

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